Switching phenomena in an annular Josephson junction

We analyze the switching to resistive state of an annular Josephson junction due to thermal activation. Mostly, we concentrate on moderate length junctions with a circumference about 10λ_J. Using a simple approximation the switching current distribution is analyzed and its standard deviation is analytically calculated. We show that the switching of the annular Josephson junction observed in recent experiments can be interpreted as a nearly homogeneous phase switching in the form of a classical string escape. Thus, in the regime close to the critical bias current, the behavior of the AJJ is similar to a small Josephson junction. Also, the deviation of the standard deviation from a T^2/3 power low and possible observation of the vortex-antivortex pair annihilation are discussed.